The major challenge facing Pfs25- and Pvs25-based transmission blocking vaccine development is to increase the immunogenicity and response longevity. In collaboration with Drs. John Robbins and Rachel Schneerson at the Laboratory of Developmental and Molecular Immunology of the NICHD, we have developed a conjugate vaccine that consists of Pfs25-Pfs25 conjugates. Various conjugation chemistries and methods were evaluated for the highest immunogenicity and most robust conjugation process. The biochemical properties of Pfs25-Pfs25 were characterized and the conjugates were evaluated in animals for their immunogenicity. The immune sera induced by the conjugate vaccine were tested for their ability to block parasite development in mosquitoes. An Investigational New Drug Application has been filed with the FDA for a planned Phase 1 trial to test safety, immunogenicity, and ex-vivo transmission blocking activity in humans.